ACTION OF THE ECDYSTEROID AGONIST TEBUFENOZIDE IN SUSCEPTIBLE AND ARTIFICIALLY SELECTED BEET ARMYWORM

Toxicity assays with tebufenozide, the first commercial non-steroidal ecdysteroid agonist, against a laboratory strain of the beet armyworm, Spodoptera exigua (Hubner), demonstrated the promise of this new comp ound for the control of this important pest. Experiments to select ins ects artificially from the laboratory strain by continuous exposure of larval instars to corresponding LC,, doses of tebufenozide for over 1 2 generations (G(0)-->G(12): 14-15 months), revealed no loss in suscep tibility to the insecticide for up to five generations. Moreover, rete ntion and fate of C-14-labelled tebufenozide were investigated using G (6) larvae from the selection experiments and the results compared wit h those for the susceptible (G(0)) larvae. In addition, piperonyl buto xide, an inhibitor of monooxygenases, when ingested by larvae along wi th tebufenozide, increased the susceptibility of intoxicated larvae to this ecdysteroid agonist, indicating its oxidative metabolism in Spod optera larvae. (C) 1998 Society of Chemical Industry.